Re: [Valgrind-users] Conflicting load reported on libstdc++ std::string

[Konstantin S. <kon...@gm...>]

On Tue, May 11, 2010 at 6:27 PM, Bart Van Assche <bva...@ac...> wrote:

> On Tue, May 11, 2010 at 11:20 AM, Konstantin Serebryany <
> kon...@gm...> wrote:
>
>>
>>> Have you already found a workaround that allows to avoid triggering
>>> the race report on std::locale::locale() ? If not, it would help if
>>> you could post a small example that allows to reproduce this behavior.
>>>
>>
>> You may like the test NegativeTests.EmptyRepTest from
>> http://code.google.com/p/data-race-test/wiki/RacecheckUnittest
>>
>> % ~/valgrind/trunk/inst/bin/valgrind --tool=helgrind
>> ./bin/racecheck_unittest-linux-x86-O0
>> --gtest_filter="NegativeTests.EmptyRepTest"
>>
>> ==28925== Possible data race during read of size 4 at 0x7fbf5b8 by thread
>> #3
>> ==28925==    at 0x7F6F3A2: std::string::erase(unsigned int, unsigned int)
>> (in /usr/grte/v1/lib/libstdc++.so.6.0.9)
>> ==28925==    by 0x804CB82: NegativeTests_EmptyRep::Worker()
>> (racecheck_unittest.cc:3168)
>> ==28925==    by 0x806E806: MyThread::ThreadBody(MyThread*)
>> (thread_wrappers_pthread.h:329)
>> ==28925==    by 0x47C4155: mythread_wrapper (hg_intercepts.c:213)
>> ==28925==    by 0x47F1024: start_thread (in /usr/grte/v1/lib/
>> libpthread-2.3.6.so)
>> ==28925==    by 0x1BD4A75D: clone (in /usr/grte/v1/lib/libc-2.3.6.so)
>> ==28925==  This conflicts with a previous write of size 4 by thread #2
>> ==28925==    at 0x7F6EC1B: std::string::_M_mutate(unsigned int, unsigned
>> int, unsigned int) (in /usr/grte/v1/lib/libstdc++.so.6.0.9)
>> ==28925==    by 0x7F6F3C6: std::string::erase(unsigned int, unsigned int)
>> (in /usr/grte/v1/lib/libstdc++.so.6.0.9)
>> ==28925==    by 0x804CB82: NegativeTests_EmptyRep::Worker()
>> (racecheck_unittest.cc:3168)
>> ==28925==    by 0x806E806: MyThread::ThreadBody(MyThread*)
>> (thread_wrappers_pthread.h:329)
>> ==28925==    by 0x47C4155: mythread_wrapper (hg_intercepts.c:213)
>> ==28925==    by 0x47F1024: start_thread (in /usr/grte/v1/lib/
>> libpthread-2.3.6.so)
>> ==28925==    by 0x1BD4A75D: clone (in /usr/grte/v1/lib/libc-2.3.6.so)
>>
>>
>> % ~/valgrind/trunk/inst/bin/valgrind --tool=drd
>> ./bin/racecheck_unittest-linux-x86-O0
>> --gtest_filter="NegativeTests.EmptyRepTest"
>>
>> ==28930==
>> ==28930== Conflicting load by thread 3 at 0x04b1f5b8 size 4
>> ==28930==    at 0x4ACEB7E: std::string::_M_mutate(unsigned int, unsigned
>> int, unsigned int) (in /usr/grte/v1/lib/libstdc++.so.6.0.9)
>> ==28930==    by 0x4ACF3C6: std::string::erase(unsigned int, unsigned int)
>> (in /usr/grte/v1/lib/libstdc++.so.6.0.9)
>> ==28930==    by 0x804CB82: NegativeTests_EmptyRep::Worker()
>> (racecheck_unittest.cc:3168)
>> ==28930==    by 0x806E806: MyThread::ThreadBody(MyThread*)
>> (thread_wrappers_pthread.h:329)
>> ==28930==    by 0x47C9BBD: vgDrd_thread_wrapper
>> (drd_pthread_intercepts.c:272)
>> ==28930==    by 0x47F7024: start_thread (in /usr/grte/v1/lib/
>> libpthread-2.3.6.so)
>> ==28930==    by 0x4BED75D: clone (in /usr/grte/v1/lib/libc-2.3.6.so)
>> ==28930== Allocation context: BSS section of
>> /usr/grte/v1/lib/libstdc++.so.6.0.9
>> ==28930== Other segment start (thread 2)
>> ==28930==    (thread finished, call stack no longer available)
>> ==28930== Other segment end (thread 2)
>> ==28930==    (thread finished, call stack no longer available)
>> ==28930==
>>
>
> Why did you post this in reply to a message about std::locale::locale() ?
> As far as I can see the race reported on the std::string object and the race
> reported on std::locale::locale() are unrelated.
>
Oops, my fault...
Indeed, a reproducer for a std::locale::locale() would be nice. I haven't
seen it so far...

--kcc


> Bart.
>